CloudFlare worker for first available YouTube thumbnail (maxresdefault or hqdefault)

ytimg.js

addEventListener('fetch', event => {
  event.respondWith(handleRequest(event.request))
});

async function fetchImage(id, type = 'maxresdefault') {
  const req = await fetch(`https://i.ytimg.com/vi/${id}/${type}.jpg`);
  if (req.status != 200) return await fetchImage(id, 'hqdefault');
  return req;
};

async function handleRequest(request) {
  const url = new URL(request.url);

  if (!url.pathname.split('/')[1]) {
    const def = await fetch('https://img.youtube.com/vi/jNQXAC9IVRw/maxresdefault.jpg');
    return new Response(def.body, def);
  }

  let videoId = url.pathname.split('/')[1]
  if (videoId.includes('.jpg')) videoId = videoId.split('.')[0];

  const image = await fetchImage(videoId);

  return new Response(image.body, image);
};

Ah got this finally.